Locking cylinder

ABSTRACT

A hydraulic cylinder and piston designed to move a load to a desired position and to lock in that position for extended periods of time, until released, even though fluid pressure to the cylinder may be interrupted, as by leakage or a break in the supply line, the locking being effected by the frictional engagement of one or more collets with the piston rod under the influence of one or more spring-biased collet closure rings.

United States Patent [72] Inventor Walter A. Sherwood Hempstead, NY.

{21] Appl. No. 776,490

[22] Filed Nov. 18, 1968 (45] Patented Apr. 13, 1971 [73] Assignee Lourdes Industries, Inc.

Farmingdale, NY.

[54] LOCKING CYLINDER 15 Claims, 3 Drawing Figs.

[52] US. Cl 92/23,

92/28(D.O.).188/67,188/170(D.O.)

[51] Int. Cl Fl5b 15/26 [50] Field of Search 92/27, 28,

[56] References Cited UNITED STATES PATENTS 2,348,764 5/1944 Thomas 92/28X 2,632,425 3/1953 Grover 92/28 2,808,903 10/1957 Kovac 188/67 3,009,747 1 1/1961 Pitzer l88/67X 3, I 76,590 4/1965 Uhtenwoldt et a1. 92/28X 3,203,513 8/1965 Allen 188/170 3,353,455 11/1967 Berry 92/27X 3,429,233 2/1969 Wright 92/27X Primary Examiner-Martin P. Schwadron Assistant Examiner-Leslie J. Payne Att0rneyNolte and Nolte LOCKING CYLINDER There are many mechanical devices wherein one part is moved to different selected positions with respect to another part by the interposition of a hydraulic cylinder and piston. If the respective parts are to hold their positions for any substantial length of time it is normally necessary to maintain the hydraulic pressure at a corresponding level or to provide a mechanical lock of some sort, the latter expedient frequently involving complex and/or not wholly reliable combinations of parts. The cylinder and piston lock disclosed herein constitutes a simple, compact and highly reliable solution to this problem.

A practical embodiment of the invention is shown in the accompanying drawing wherein:

FIG. 1 represents an axial sectional view of a cylinder and piston provided with locking means;

FIG. 2 represents a detail sectional view showing an alternative form of locking means, parts being broken away and parts being omitted; and

FIG. 3 represents graphically the parameters involved in the design of the locking means.

Referring to the drawings, the cylinder has a bore 11 in which the piston 12 is slidable, the piston being provided with sealing means 13 to prevent leakage of hydraulic fluid past the piston head. The piston rod 14 extends from one end of the cylinder through a sealed opening 15, into and beyond the locking chambers 16, 17 and free end 18 of the piston being engageable with a part to be moved. Socket 19 represents a point of attachment for the piston to a mechanical part subject to movement relative to the cylinder; for present purposes it will be assumed that the cylinder is to be fixed and that a load is to be moved by the piston.

The locking chamber 16 is shown as containing resilient drive means in the form of a spring 21 under compression between the end 22 of the chamber and an annular unlocking piston 23 which surrounds the piston rod 14 and sealingly engages said rod and the wall of the chamber 16. The locking chambers 16 and 17 are separated by the provision of an annular shoulder 24 integral with the locking chamber wall and shown as having beveled surfaces 25, 26 facing each of the locking chambers.

Between the unlocking piston 23 and the shoulder 24 there are a plurality of collets 27, 27' (two being shown) each having double beveled outer surfaces, and a plurality of collet compression rings, the first one 28 having a beveled inner surface with the same angle as the adjacent collet surface and the next ring 28 having double beveled inner surfaces and being disposed between the collets 27 and 27. The collet 27 nearest the shoulder 24 has one beveled surface engageable with the surface and disposed at the same angle.

The locking chamber 17 is provided with elements corresponding to those just described but complementary thereto, the spring 29 being under compression between the end 30 of the chamber and an unlocking piston 31, collets 32, 32' and collet locking rings 33, 33' being disposed.

The cylinder 10 is provided, at suitable points, with ports for admission of hydraulic fluid under pressure, the piston extending port being designated 34 and the piston retracting port being designated 35. The shoulder 24 is traversed radially by a fluid passage 36 communicating with the port 37 for admission of fluid under pressure for unlocking the piston whenever it is to be moved either by its load or by fluid admitted through ports 34 or 35. The source or sources of hydraulic fluid and valves to control its admission and discharge are conventional and not shown. If adequate shaft seals are provided at the ends 22 and 30 of the locking chambers, the springs 21 and 29 could be replaced by bodies of air compressed to a pressure less than that of the fluid supplied through the port 37, in accordance with known practice in the accumulator art.

In operation, it will be understood that the system is normally locked, in any position, except when deliberately unlocked. The locking action, for example against the force of a load on the piston rod tending to cause retraction, results from the force of the spring 21 acting on piston 23 which urges compression ring 28 toward the adjacent collet 27. The engagement of the beveled surfaces of collet 27 and ring 28 causes compression of the collet against the piston rod so that the collet is urged toward the ring 28 also by frictional engagement with the piston rod. The compression ring 28 bears against the second collet 27 compressing it into engagement with the piston rod with a force which includes that originating in the spring and that due to engagement of collet 27 with the piston rod. The locking forces thus increase cumulatively with the collet 27' hearing against the beveled surface 25 of the collar 24, and the actual movement of the piston rod involved in the generating of said forces is very slight and quite predictable.

If the piston rod is subjected to a load tending to extend it, the spring 29, piston 31, collets 32, 32' and rings 33, 33 in the chamber 17 operate as just described to prevent such movement.

To unlock the piston it is only necessary to admit fluid through the port 37 and passage 36 into the space between shoulder 24 and the piston rod. The fluid will force the adjacent collets out of engagement with the faces 25, 26 of the shoulder 24 and will then exert pressure on the unlocking pistons 23 and 31, counteracting the pressure of springs 21 and 29 so that the collets and compression rings are no longer squeezed together and the collets relax their engagement with the piston rod. The piston can then be freely extended or retracted by supplying fluid to the cylinder through ports 34 or 35, and can also be locked instantly in any position by relieving the fluid pressure through port 37.

In the alternative form of FIG. 2 the spring 40 urges the unlocking piston 41 against the flat radial surface 42 of a first collet 43, the single bevel 44 of which bears against the complimentary single bevel 45 of the first compression ring 46. Each collet and each compression ring, in this form, is beveled only on one side, the flat radial surface 47 of the first compression ring 46 bearing on a flat radial surface of the second collet, and so on through the series of alternating collets and compression rings on each said of the shoulder 48. The last collet on each side of the shoulder has its beveled surface bearing against a corresponding surface of the shoulder, as in the form of FIG. 1. Hydraulic fluid pressure is admitted through the port 49, when desired, to drive back the unlocking pistons and relieve all the collets of the locking forces communicated by their respective compression rings.

The relation of the forces applied and developed in the locking operation of the mechanism shown in FIG. 2 is graphically illustrated in FIG. 3. A constant force Kx is applied to the unlocking piston (not shown) by the spring (not shown), this force being translated by the engagement of the beveled surfaces of the collet C and compression ring R into a locking force tan 0 applied by the collet to the piston rod. If a load F on the piston rod tends to move it in the same direction as the spring force this tendency is communicated to the ring R which reacts with a force ftan 0 and is thus urged toward the next following collet and ring with a force Kit .4 tan 0 and the cumulation of locking forces continues through the whole series. Since the gripping forces increase in the direction toward the fixed shoulder there is no possibility of relaxation at any point until the spring pressure, which initiated the operation and is essential for maintaining it, is released. When the factor K): is eliminated each collet will release its grip on the piston rod, leaving the piston free to be advanced or retracted to a new position, as desired.

While the locking means is described in connection with a hydraulic cylinder and piston, it will be understood that it could be applied to any shaft which is slidable to selected adjusted positions and designed to be locked therein against movement under an applied axial load. if the anticipated load is uniformly from one direction, only the collets and compression rings on the side responding to such a load are needed.

The hydraulic cylinder is designed to be mounted in any suitable manner on the frame or base toward or away from which a load is to be moved and the end of the piston rod is designed to be connected to a load (or frame bearing a load), The cylinder and piston are actuated to position the load as precisely as desired-the locking elements being in unlocking relation during such positioningand when said elements are returned to locking relation the position of the load is maintained against any anticipated forces. in an assembly of the type illustrated having a piston rod 1% inches in diameter the locking withstands loads up to 17,000 lbs. or more. Since the locking action is mechanical it is not materially affected by extreme variations in climatic conditions including heat, cold, moisture, etc. The mechanism is thus useful, for instance, in such items of ordnance as rocket launchers.

lclaim:

t. A shaft slida'ole through a housing to selected adjusted positions with respect to said housing in combination with releasable locking means adapted to hold the shaft in each adjusted position against an applied axial load comprising, a fixed abutment within the housing, a plurality of collets bearing against the shaft, each collet having at least one beveled outer surface, at least one compression ring having a beveled inner surface complementary to and bearing against the beveled outer surface of an adjacent collet, resilient drive means biased to urge said collets and ring toward said abutment and into shaft locking position, the collet nearest said drive means engaging tightly with the shaft and transmitting additional locking force from the shaft to an adjacent collet the locking force applied representing the sum of the forces developed and transmitted by the arrangement of the components of said locking means in cooperation with said shaft, and unlocking means adapted to be actuated to counter act the bias of said drive means.

2. The shaft loclting combination according to claim l in which the fixed abutment is provided with a beveled inner surface complementary to and bearing against the beveled outer surface of an adjacent collet.

3. The shaft locking combination according to claim 2 in which each collet has two oppositely facing beveled outer surfaces and at least one compression ring has oppositely facing beveled inner surfaces.

3. The shaft locking combination according to claim 3 which includes a second compression ring having a single beveled inner surface complementary to and bearing against a beveled outer surface of a collet.

5. The shaft locking combination according to claim l in which the resilient drive means is a spring under less than maximum compression.

6. The shaft locking combination according to claim l in which the fixed abutment is located intermediate the ends of the housing and which includes a plurality of collets as claimed on each side of said fixed abutment, at least one compression ring as claimed on each side of the abutment, resilient drive means as claimed on each side of the abutment, and in which the unlocking means is associated with said abutment, the respective beveled surfaces on one side of the fixed abutment being disposed oppositely with respect to the beveled surfaces on the other side of the abutment.

7. The shaft locking combination according to claim 6 in which the fixed abutment is provided with beveled inner surfaces on each side complementary to and bearing against the beveled outer surface of an adjacent collet. v

G. The shaft locking combination according to claim 7 in which each collet has two oppositely facing beveled outer surfaces and at least one compression ring on each side of the abutment has oppositely beveled inner surfaces.

J. The shaft locking combination according to claim ii which includes a second compression ring on each side of the abutment and having a single beveled inner surface complementary to and bearing against a beveled outer surface of a collet.

lb. The shaft locking combination according to claim 0 in which the resilient drive means is a spring under less than maximum compression.

if. The shaft locking combination according to claim l in which each collet has a single beveled outer surface and a flat radially disposed side face and each compression ring has a single beveled inner surface and a flat radially disposed side face.

H2. The shaft locking combination according to claim it in which the fixed abutment is provided with a beveled inner surface complementary to and bearing against the beveled outer surface of an adjacent collet.

l3. The shaft locking combination according to claim it in which the fixed abutment is located intermediate the ends of the housing and which includes a plurality of collets as claimed on each side of said fixed abutment, at least one compression ring as claimed on each side of the abutment, resilient drive means as claimed on each side of the abutment, and in which the unlocking means is associated with said abutment, the respective beveled surfaces on one side of the fixed abutment being disposed oppositely with respect to the beveled surfaces on the other side of the abutment.

The shaft locking combination according to claim lit in which the fixed abutment is provided with beveled inner surfaces on each side complementary to and bearing against the beveled outer surface of an adjacent collet.

H5. The shaft locking combination according to claim l which includes a hydraulic cylinder and piston, said slidable shaft being a piston rod attached to said piston. 

1. A shaft slidable through a housing to selected adjusted positions with respect to said housing in combination with releasable locking means adapted to hold the shaft in each adjusted position against an applied axial load comprising, a fixed abutment within the housing, a plurality of collets bearing against the shaft, each collet having at least one beveled outer surface, at least one compression ring having a beveled inner surface complementary to and bearing against the beveled outer surface of an adjacent collet, resilient drive means biased to urge said collets and ring toward said abutment and into shaft locking position, the collet nearest said drive means engaging tightly with the shaft and transmitting additional locking force from the shaft to an adjacent collet the locking force applied representing the sum of the forces developed and transmitted by the arrangement of the components of said locking means in cooperation with said shaft, and unlocking means adapted to be actuated to counter act the bias of said drive means.
 2. The shaft locking combination according to claim 1 in which the fixed abutment is provided with a beveled inner surface complementary to and bearing against the beveled outer surface of an adjacent collet.
 3. The shaft locking combination according to claim 2 in which each collet has two oppositely facing beveled outer surfaces and at least one compression ring has oppositely facing beveled inner surfaces.
 4. The shaft locking combination according to claim 3 which includes a second coMpression ring having a single beveled inner surface complementary to and bearing against a beveled outer surface of a collet.
 5. The shaft locking combination according to claim 1 in which the resilient drive means is a spring under less than maximum compression.
 6. The shaft locking combination according to claim 1 in which the fixed abutment is located intermediate the ends of the housing and which includes a plurality of collets as claimed on each side of said fixed abutment, at least one compression ring as claimed on each side of the abutment, resilient drive means as claimed on each side of the abutment, and in which the unlocking means is associated with said abutment, the respective beveled surfaces on one side of the fixed abutment being disposed oppositely with respect to the beveled surfaces on the other side of the abutment.
 7. The shaft locking combination according to claim 6 in which the fixed abutment is provided with beveled inner surfaces on each side complementary to and bearing against the beveled outer surface of an adjacent collet.
 8. The shaft locking combination according to claim 7 in which each collet has two oppositely facing beveled outer surfaces and at least one compression ring on each side of the abutment has oppositely beveled inner surfaces.
 9. The shaft locking combination according to claim 8 which includes a second compression ring on each side of the abutment and having a single beveled inner surface complementary to and bearing against a beveled outer surface of a collet.
 10. The shaft locking combination according to claim 6 in which the resilient drive means is a spring under less than maximum compression.
 11. The shaft locking combination according to claim 1 in which each collet has a single beveled outer surface and a flat radially disposed side face and each compression ring has a single beveled inner surface and a flat radially disposed side face.
 12. The shaft locking combination according to claim 11 in which the fixed abutment is provided with a beveled inner surface complementary to and bearing against the beveled outer surface of an adjacent collet.
 13. The shaft locking combination according to claim 11 in which the fixed abutment is located intermediate the ends of the housing and which includes a plurality of collets as claimed on each side of said fixed abutment, at least one compression ring as claimed on each side of the abutment, resilient drive means as claimed on each side of the abutment, and in which the unlocking means is associated with said abutment, the respective beveled surfaces on one side of the fixed abutment being disposed oppositely with respect to the beveled surfaces on the other side of the abutment.
 14. The shaft locking combination according to claim 13 in which the fixed abutment is provided with beveled inner surfaces on each side complementary to and bearing against the beveled outer surface of an adjacent collet.
 15. The shaft locking combination according to claim 1 which includes a hydraulic cylinder and piston, said slidable shaft being a piston rod attached to said piston. 